Different Methods Of Liposome Manufacturing

By Jody Leach


Liposomes have attracted much attention since they were first discovered. These artificially created, microscopic spheres have many properties that make them extremely useful. One of these is their bio-compatibility. They act in exactly the same way as the cellular membranes of the body. This means they can be used as a unique delivery system for nutrients, drugs and other agents to specific areas in an organism. There are a numbers of ways in which liposome manufacturing is achieved, all of which have advantages and disadvantages.

Formation of liposomes is not spontaneous. Lipid vesicles are formed when phospholipids like lecithin are placed in water. Each molecule has a water-loving head and two water-repelling tails. When these molecules are placed in a water-based solution, the heads line up side by side with the tails behind. The fact that the tails are repelled by water means that another layer lines up with the tails facing one another. These two rows form a protective membrane around the cell.

Liposomes can be used as delivery vehicles for a wide variety of drugs, vaccines, enzymes, genetic material and for some nutritional supplements as well. They not only allow for release of encapsulated materials but are beneficial in themselves for cells. The lipids used to construct the fatty part of the molecule is used by the cell wall for repair and construction of new membranes.

Various lipids and mixtures can be used to make liposomes and some of these are of a higher quality than others. What they have in common is they do not go through the digestive tract and the encapsulated payload is not biologically active until it reaches the cells. It is how, when, where and why the rupture of the membrane occurs that the difference between them comes in.

The methods used in preparation may all be quite different but the basic stages remain the same. Thin lipid films are hydrated and this causes liquid bilayers to form. These large vesicles need to be reduced in size and energy output is required for this. Sonication is the use of sound waves and another mechanical method used is extrusion.

Liposomes are actually fairly simple to make, not requiring complex materials, equipment or methods. Each method and technique offers certain benefits and has some failings. Sonication can cause structural changes to what is entrapped. Liquid hydration methods do not produce a high payload.

Some of the problems associated with these processes are inconsistencies in size, structural instability and high costs. These problems are all receiving attention and solutions are being found. Cosmetology, for example, is benefiting from the production of tiny particles called nanosomes which are much, much smaller than normal liposomes and can therefore penetrate the skin more easily.

A great benefit involved in using liposomes is that they can be customized for different applications by varying the method of preparation, size, lipid content and surface charge. Many conventional techniques for preparing them and reducing their size are fairly simple to implement and equipment does not have to be too sophisticated. However, novel routes are being discovered for preparation due to motivation to scale-down for point-of-care applications or or to scale-up for industrial applications.




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